Dr S-005, also known as the “Bad Doctor”, was one of the prisoners, arrested for illegal experimentation into enhanced cybernetics. Upon waking up in the wake of the crash, he remembered cybernetics and knew himself to be an expert on the field, but he couldn't quite remember how to do them, and so decided to try and learn it by cutting people open and examining their nervous systems.
Early on, while most people still haven't quite recovered their ability to form long term memories1) he found a pair of people who decided to stick together after waking up with no memories and got them to help him collect useful equipment. He never bothered to learn their names, so in his head and here they will be referred to as Escaped Experiment #1 and Escaped Experiment #22), or #1 and #2 for short. Once he had all the equipment he needed, the only thing left that he needed was test subjects, and #1 and #2 both fulfilled that role admirably. Or at least, he had hoped so, but the building he chained them up in was a bit structurally unsound, so #1 was able to escape, and promptly forgot all about S-005 and #2 because long-term memories were still problematic. So S-005 found some other poor shmucks to help him move everything out of town to an abandoned Heizar building on a sometimes-island and promptly captured them as well, spending the next year or so experimenting on them and other test subjects how the human nervous system worked and how their limbs worked, in the hopes of recreating his cybernetics research3).
There were plans/thoughts on his notes unlocking the ability to make the Enhanced Cybernetics, which would essentially work as some sort of Enhanced Strength quirk, at the cost of being immensely painful and degrading if used as enhanced strength. Since no one actually read the notes we never fully fleshed out the idea.
For some people, the release from the cryopods was not as smooth as it was for others. While most got away with merely memory loss, others suffered severe nerve damage which prevented them from feeling pain. If you took this Quirk, that was you.
This was a negative Quirk that prevented you from telling how injured you were, with the original idea being that if you don't realise your leg is broken, you would keep walking on it and making it worse.
The Quirk could also have been cured using the Neurology skill, which we tried to hint at in several places but apparently didn't quite get the message across (or didn't get it to the right people).